/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/NiagaraNode.h
If the pin is a known name (like Engine.DeltaTime) this tries to return a default tooltip for it.
bool GetTooltipTextForKnownPin ( const [UEdGraphPin](API\Runtime\Engine\EdGraph\UEdGraphPin) & Pin, [FText](API\Runtime\Core\Internationalization\FText) & OutTooltip ) const